Catalysts comprising cobalt on a support such as silica or alumina are known in the art for hydrogenation reactions, e.g. for the hydrogenation of chemicals such as aldehydes and nitriles and for the preparation of hydrocarbons from synthesis gas via the Fischer-Tropsch reaction.
WO-A-96/04072 discloses a cobalt on transition alumina catalyst containing between 3 and 40% by weight of cobalt and having a cobalt surface area greater than 30 m2/g cobalt.
EP-A-0013275 discloses coprecipitated cobalt-silica hydrogenation catalysts prepared by adding an alkaline precipitating agent to a heated mixture containing cobalt cations, silicate anions and solid porous carrier particles under agitation thereby to precipitate the cobalt and silicate ions onto the solid support particles.
WO-A-02/089978 describes a catalyst for use in the Fischer-Tropsch process, comprising at least one metal selected from the group consisting of nickel, cobalt, iron, ruthenium, osmium, platinum, palladium, iridium, rhenium, molybdenum, chromium, tungsten, vanadium, rhodium, copper, zinc, and combinations thereof and at least one promoter, said metal and promoter being dispersed on a support to form a catalyst particle. The preferred support is alumina. The particles have a BET surface area of from about 100 m2/g to about 250 m2/g, and the metal and promoter are dispersed on the support such that the crystallite size of the metal oxide is from about 40 Å to about 200 Å.
In certain reactions it may be beneficial to use cobalt deposited on a titania support rather than cobalt on alumina. For example, as reported by Oukaci et al (Applied Catalysis A: General 186 (1999) 129-144)), cobalt supported on titania is preferred by some workers for Fischer-Tropsch reactions because it is more active for CO hydrogenation than cobalt catalysts supported on alumina or silica or other supports. Furthermore titania supported catalyst may be preferred for use in acid reaction media where gamma alumina supports may show a tendency to dissolve to some extent.
U.S. Pat. No. 5,968,991 describes a process for the preparation of a catalyst useful for conducting carbon monoxide hydrogenation reactions, especially a Fischer-Tropsch catalyst. In the preparation of the catalyst, a solution of a multi-functional carboxylic acid having from about 3 to 6 total carbon atoms, especially glutamic or citric acid, is employed to impregnate and disperse a compound or salt of rhenium and a compound or salt of a catalytic metal, or metals, e.g., copper or an Iron Group metal such as iron, cobalt, or nickel onto a refractory inorganic oxide support such as titania. This method of preparation requires repeated impregnations in order to achieve the desired cobalt loadings.
U.S. Pat. No. 6,130,184 describes a process for the preparation of a cobalt-containing catalyst or catalyst precursor, comprising mixing titania or a titania precursor, a liquid, and a cobalt compound, which is at least partially insoluble in the amount of liquid used, to form a mixture, shaping and drying of the mixture thus-obtained, followed by calcination.
U.S. Pat. No. 5,545,674 describes a process for preparing cobalt catalysts supported on titania spheres by spraying the hot titania spheres with an aqueous cobalt nitrate and perrhenic acid mixture, optionally after soaking the support spheres in a non-aqueous liquid to provide a non-uniformly distributed cobalt catalyst.
U.S. Pat. No. 4,595,703 describes a cobalt-titania catalyst, or thoria promoted cobalt-titania catalyst used in a Fischer-Tropsch process wherein cobalt, or cobalt and thoria, is composited, or dispersed upon titania, TiO2, or a titania-containing carrier, or support, wherein the support contains a rutile:anatase ratio of at least about 2:3, and preferably at least about 3:2.
In comparison with other catalytic metals such as copper and nickel used for hydrogenation reactions, cobalt is a relatively expensive and so, to obtain the optimum activity, it is desirable that as much as possible of the cobalt present is in an active form accessible to the reactants. It is therefore desirable to maximise the surface area of the cobalt in the supported catalysts. It is desirable to manufacture a cobalt catalyst supported upon titania which is useful in the Fischer-Tropsch process by depositing a relatively high loading of well-dispersed cobalt species upon the support.